1. Field of the Invention
The present invention relates to a laser scanning unit module applied to a printer, and more particularly, to a laser scanning unit module having a memory for storing information required for laser scanning control of the laser scanning unit.
2. Description of the Related Art
Referring to FIG. 1, a conventional color printer comprises a photosensitive belt 14 circulating around three rollers 11, 12 and 13 arranged at three corners, and a reset device 15, laser scanning units 16, developing units 17, a drying device 18 and a transferring device 20 which are arranged adjacent to the circulating path of the photosensitive belt 14.
In a printing operation, each laser scanning unit 16 irradiates light corresponding to an image to be printed on a predetermined region of the photosensitive belt 14 passing by the reset device 15 while the photosensitive belt 14 circulates. During this process, an electrostatic latent image is formed in the photosensitive belt 14. The developing units 17 provide a solid developing material, toner, or a developing solution to the region of the photosensitive belt 14 in which the electrostatic latent image has been formed, thereby developing the electrostatic latent image into a toner image. As the photosensitive belt 14 continues to circulate, the toner image is transferred onto a transferring roller 21 from the photosensitive belt 14. The image transferred onto the transferring roller 21 is transferred again onto a paper 23 which is fed between the transferring roller 21 and a press roller 22, so that an intended image is printed onto the paper 23.
In the operation of the above printing process, in order to obtain a distinct color image without misregistration, it is necessary to synchronize the start of scanning of the laser scanning units 16 such that the laser scanning units 16 arranged a predetermined distance apart can irradiate light onto a predetermined region of the belt, respectively.
According to the prior art, the scanning synchronization of each laser scanning unit 16 is controlled by the following method.
First, after a printer is completely assembled, an image having a predetermined test pattern is printed as a test. Then, a tester physically measures the distance between each color pattern, from the obtained print. Based on the distance between each color pattern, the scanning start timing of each laser scanning unit 16 and the emission interval between light beams per pixel are adjusted, and the adjusted data are input to a lookup table (not shown) used to control the scanning synchronization.
However, the conventional control method for the scanning synchronization requires repeated test printings to achieve precise controlling by minimizing errors manipulated by the test printing. Thus, it takes a long time to obtain the data for precise scanning synchronization. Also, because the scanning characteristics of the laser scanning units 16 are evaluated from the printed result, the above process must be performed again after assembly or replacement of the laser scanning units.